Synergistic creation of highly stable strain-insensitive pressure sensors by in-plane strain modulation and quasi-homogenous interfacial design

Abstract

The urgent requirement of electronic skin conformably attached to nonplanar surfaces to provide stable monitoring in areas of healthcare, prosthetics, and robotics promotes the development of strain-insensitive/unperturbed pressure sensors. The main challenges lie in: (1) stretchability and conductive stability of flexible electrodes and (2) mechanical stability of heterogeneous interfaces. This study presents a highly stable strain-insensitive pressure sensor achieved by in-plane strain modulation and quasi-homogenous interfacial design. Strain modulation of stretchable electrodes by both periodic microstructured engineering and pre-stretching strategies (called “island-ripple”) was employed to suppress microcracks propagation. The improvement in stretchability and cyclic conductive stability of electrodes was identified by finite element analysis and experimental verification. The pre-stretched microconed stretchable electrode with a low sheet resistance of 0.546 Ω sq−1 shows a maximum deformation of up to 80% and excellent cyclic conductive stability over 10000 times under 30% strain. Quasi-homogenous interface strategy by the CNTs/PDMS system was employed to enhance the mechanical and electrical stability of the electrode-active materials interface, demonstrating a strong peel strength and shear strength of >40.9 N/m and >124.8 kPa, respectively. The as-prepared strain-insensitive pressure sensor provides constant sensing performance over 5000 stretching-releasing cycles within 20% stretching. In addition, a 4 × 4 pixel strain-insensitive pressure sensor array with reduced cross-talk circuit design was further integrated to identify the shape and weight of different objects under strains. The stretchability and stability of our sensor enable it to be applied in stretchable electronics with great potential.